Contact units and electromechanical switching devices of the generic type are known in principle, and therefore separate documentary evidence of this is not required. Electromechanical switching devices of the generic type are used to interrupt and, respectively, to close electrical circuits in a predefinable manner by providing an electromechanical switching contact, depending on a switching state of the switching contact. To this end, said electromechanical switching devices can comprise a manually and/or an automatically operable drive unit by means of which the switching contact can be moved to the desired switching state. The drive unit operates at least one of the contact units in order to be able to provide the desired switching state in the electromechanical switching device. Electromechanical switching devices of the generic type comprise, for example, single- or multiple-pole electromechanical switches which can be operated, for example manually, by means of an operating element. The operating element can be used to change from one switching state of the electronic mechanical switching device to another switching state of the electromechanical switching device. If the operating element is designed for manual operation, it can be formed, for example, by a pushbutton, a switching lever, a rotary lever, combinations of these and/or the like. If automatic operation is provided, the drive unit can also be designed in such a way that it can be operated in a magnetic, electrical, pneumatic and/or hydraulic manner or the like in order to be able to provide a desired switching state of the electromechanical switching device. A drive unit for magnetic operation is present, for example, in a relay, a contactor or the like.
The contact unit of the electromechanical switching device serves to provide a contact surface by means of the contact element which is connected to the carrier element, wherein the respective contact areas mechanically touch or are positioned in a manner physically spaced apart from one another by virtue of a mechanical movement of the carrier element with the contact element depending on the respective switching state of the electromechanical switching device. An electrically conductive connection can be established in the switching state in which contact is made between the contact areas. The electrical connection is interrupted in the spaced-apart state.
Electromechanical switching devices of the generic type and corresponding contact units are used, in particular, in low-voltage switch disconnectors, low-voltage circuit breakers and/or the like. In the prior art, it is customary to use a silver-based material which forms the respective contact element and provides the respective contact area. Furthermore, the silver-based layer comprises a small proportion of graphite.
In electromechanical switching devices, contact materials are usually intended to realize contact resistances which are as low as possible when the electromechanical switching device is in the switched-on state. However, at the same time, a low level of material loss and also a low tendency to weld are intended to be achieved during operation as intended. However, these properties contradict one another. Although the silver-based contact material with the addition of graphite has proven expedient, there is still a need for improvement, in particular with respect to the durability of the switching device and reliable operation.